Seat suspension arrangements

ABSTRACT

A seat suspension arrangement comprising a seat frame ( 5 ), upholstery supporting means ( 1, 3 ) suspended transversely between lateral margins ( 5   a ) of the seat frame ( 5 ) and adjustable link means ( 7 ) for varying the transverse tension in the upholstery supporting means ( 1, 3 ) to vary the effective profile of the support provided by said upholstery supporting means ( 1, 3 ), wherein a plurality of said adjustable link means ( 7 ) are provided, spaced apart in a direction parallel to said lateral margins ( 5   a ) of the seat frame ( 5 ), and means is provided for enabling adjustment of the relative lengths of said plurality of link means ( 7 ) in such a manner that the profile of the support can be varied, both to adjust the degree of support provided at a given point, and also to adjust the position of the point at which said support is provided.

This invention concerns improvements in or relating to seat suspensionarrangements of the kind enabling the contour of the support provided bya seat to be adjusted by the user. The arrangement is particularlyintended for use in the backrest of a vehicle seat to provide adjustablelumbar support, but it will be appreciated that the principle may beapplied to any other arrangement wherein the contour of a seat cushionis desired to be adjusted, for example to a seat base having means forproviding adjustable thigh support.

The present invention has particular reference to a seat suspensionarrangement of the kind described and claimed in our co-pendingInternational Patent Application No PCT/EP97/04580 (Publication No WO98/07590) the contents of which are included herein by this reference.The invention is not limited to application in this context, however.

Arrangements of the kind referred to above are applicable to seatshaving upholstery supporting means suspended transversely in the seat tosupport the seat upholstery, and make use of tensioning elements in theform of one or more adjustable links that can serve to vary the degreeof tension in the upholstery supporting means suspended in the seatframe in a given region, for example the lumbar region, to causevariation in the profile of the upholstery support. The adjustable linksare advantageously provided by Bowden cables.

When such an arrangement is applied to a seat back to provide adjustablelumbar support, it gives lumbar adjustment in a horizontal direction.However there is an increasing demand for vehicle seats with so-called“four way” lumbar adjustment in which the lumbar supporting area of theseat can be moved to and fro, not only in the horizontal direction, butalso vertically.

The additional vertical adjustment has been provided in some knownarrangements by arranging for vertical movement of the upholsterysupporting means itself as a unit in order to move the point of lumbarsupport. However such an arrangement is relatively complicated andexpensive and would in any case be very difficult to apply to a Bowdencable actuated mechanism of the kind under consideration.

It is therefore an object of the invention to provide an improvedarrangement of the kind using tensioning elements in the form ofadjustable links to adjust the contour of a seat support in which moreversatile adjustment of the contour of such a platform element ispossible.

According to the invention there is provided a seat arrangementcomprising a seat frame, upholstery supporting means suspendedtransversely between lateral margins of the seat frame and adjustablelink means for varying the tranverse tension in the upholsterysupporting means between said margins at a given point in order to varythe effective profile of the support provided by said supporting means,wherein a plurality of said adjustable link means are provided, spacedapart in a direction parallel to said margins of the seat frame, andmeans is provided for enabling adjustment of the relative lengths ofsaid plurality of link means in such a manner that the profile of thesupport can be varied, both to adjust the degree of support provided ata given point, and also to adjust the position of the point at whichsaid support is provided.

A preferred embodiment of the present invention comprises a seat frameand a platform element adapted to provide support for upholstery of theseat, the platform element being linked to the seat frame by adjustablelink means disposed at two or more locations along at least one marginof the platform element, the said platform element being so constructedthat it is resiliently extensible in a direction towards said margin ofsaid seat frame, means being provided for adjusting the effective lengthof said link means, the arrangement being such that with the link meansin an extended condition at at least one of the said two or morelocations on the margin of the platform element at least one portionthereof is recessed relatively to a boundary of the seat frame formingan attachment for the link means, and said adjustable link means beingsupplemented by further non-adjustable link means for retaining theposition of the margin of said platform element relatively to the seatframe whereby upon contraction of the adjustable link means said portionof the platform element is displaced towards said boundary in order tovary the contour of the said platform element.

The adjustable link means may conveniently be provided for each sidemargin of the platform element at at least two locations on each saidside margin.

The adjustable link means for the or each margin may be provided with aseparate mounting bracket at each location or may be provided with acommon mounting bracket spanning the locations at each margin.

Advantageously the means for adjusting the effective length of theadjustable link means are formed of Bowden cables suitably mounted inthe brackets referred to above and may be manually actuable or in thealternative may be actuated by one or more suitable power packscontrollable by the seat user according to personal preference.

By way of example only one embodiment of seat suspension arrangementaccording to the invention is described below with reference to theaccompanying drawings in which:

FIG. 1 is a front elevation of a seat suspension platform for a seatback of a vehicle, shown in place in a seat frame together with anassociated adjusting arrangement, showing a lumbar region of thesuspension platform in a first condition;

FIG. 2 is a sectional elevation on the line II—II in FIG. 1;

FIG. 3 is a perspective front view corresponding to FIG. 1 showing alumbar region of the platform element in a first condition;

FIG. 4 is a front elevation of the seat suspension platform of FIG. 1showing a lumbar region of the suspension platform in a secondcondition;

FIG. 5 is a sectional view on the line VI—VI of FIG. 4;

FIG. 6 is a perspective front view corresponding to FIG. 4 showing alumbar region of the platform element in a second first condition;

Referring to the drawings, a platform element for supporting theupholstery of a vehicle seat back comprises a pair of side rails 1formed in known manner of paper wrapped or plastic coated steel wire,the side rails being bent over at their relatively upper and lower endsas shown.

Between the side rails 1 are provided a plurality of transversesupporting wires 3 which are angled at 3A so that they form sinuous wiresprings allowing for limited transverse stretching of the platformelement. The wires 3 are anchored to the rails 1 by being wound aroundthe latter in such a manner that they compress the paper or plasticcovering of the side rails and are thereby retained in theirlongitudinal spacing. The longitudinal pitch of the wires 3 is varied inaccordance with the desired support characteristics to be provided bythe platform element, and the transverse supporting wires 3 penetrateand are interconnected centrally by means of a longitudinal cord 4.

A seat frame is indicated at 5 and the platform element is suspended inthe seat frame at spaced apart locations by means of non-adjustable wirelinks 6 which in this example are extensions of selected wires 3 whichare reeved around the rails 1 and are attached as at 6A at a pointtowards the rear boundary of the side pillars 5A of the frame 5 as canbe seen more clearly in FIGS. 3 and 6. It will be appreciated that thewire links 6 in alternative embodiments may be separate from the wires 3and may for example be of a form disclosed in the said co-pendingInternational Application.

In the region of the platform element that is intended to provide lumbarsupport for the occupant of the seat, there is attached to each siderail 1 a sheet metal bracket 7 which has lugs 7A engaging the rail andalso providing two spaced anchorages for the outer sheaths 8 of twoBowden cables 9. The cables 9 are coupled to one or more poweredactuators 30 situated within a side pillar 5A of the seat frame 5. Acontrol (not shown) for the actuator(s) is provided in a suitablelocation for ease of access by the occupant of the seat. It will beunderstood that in an alternative embodiment of the present invention amanual actuator such as that designated generally at 10 in ourco-pending International Patent Application could be adopted.

The cables 9 extend through the bracket 7 and are connected to a frontboundary of the side pillars 5A of the frame 5 and effectively act aswire links determining the positions of the adjacent portions of theside rails 1 relatively to the seat frame 5.

Thus by operation of the power actuators 30 the Bowden cables can beretracted relatively to the brackets 7, thus shortening the linkscoupling the side rails 1 to the frame 5 at these points.

Referring more particularly to FIGS. 1 to 3, the platform element isshown in a first condition in which the lumbar region is in a supportmode with the wires 3 being contoured outwardly as at 40. The degree ofoutward extension of the wires 3 is governed by the tension applied bytie Bowden cables and accordingly the maximum lumbar support is providedwhen the tension is at a maximum level thereby tensioning the platformelement forwardly as can clearly be seen from FIG. 3 at the level of thebrackets 7. Since the wire links 6 are non-adjustable and limited intheir extension capacity, they prevent displacement of the remainder ofthe platform element.

Referring now to FIGS. 4 to 6, it will readily be observed that theplatform element has assumed a second condition in which the lumbarregion is relatively flat as at 42. In this condition, the tension inthe Bowden cables 9 has been relaxed to reduce the level of tie contourthereby reducing the degree of lumbar support.

It will be appreciated that by varying the tension in the cables eitherin unison or individually the contour of the lumbar region can be variedcorrespondingly to provide a customized profile for the individualoccupant of the seat. More particularly by selecting the relativetension that is applied to each of the cables the effective point oflumbar support can be moved vertically by correspondingly profiling theplatform element so that the abovementioned “four way” adjustment can beachieved without the need for vertical movement of the platform elementitself.

It will be understood that whilst the invention has been described withparticular reference to link means provided at two locations on eachside rail, further adjustable link means may be provided on each railaccording to the particular requirements. Furthermore althoughadjustable link means are provided on each side of the seat frame, in aneconomy version they may be provided on only one side of the seat. Itwould also be possible, instead of providing adjustable link means atthe lateral margins of the platform element, to divide the platformelement vertically at its centre and to arrange the adjustable linkmeans within the boundaries of the supporting surface provided by theplatform element.

What is claimed is:
 1. A seat arrangement comprising: a seat frame (5)providing a seat back; an upholstery supporting means comprising aplatform element formed by a pair of spaced apart side rails (1) betweenwhich are anchored transverse supporting elements (3) that areresiliently extensible to allow limited transverse stretching of theplatform element; the side rails (1) being linked to the seat frame (5)by substantially inextensible link means (6), and also being linked byadjustable link means (9) which are operable for tensioning saidtransverse supporting elements (3) via at least one of said side rails(1) to provide adjustable lumbar support in the back seat; at least twoof said adjustable link means being provided at intervals spaced apartin the longitudinal direction of the seat back, and the spaced apartadjustable link means being individually operable such that differentialadjustment of said spaced apart link means varies the profile of theplatform element to provide a lumbar support that is adjustable both indegree and in position along the longitudinal axis of the platformelement.
 2. A seat arrangement according to claim 1, wherein each ofsaid side rails (1) is linked to one side of the seat frame (5), betweenadjacent longitudinally spaced inextensible link means (6), by theadjustable link means (9), the profile of each of the side rails (1) inthe region between the non-extensible link means (6) being variable byrelative tensioning of the two adjustable link means (9).
 3. A seatarrangement according to claim 2, wherein points of attachment of saidadjustable link means to said side rails (1) are recessed in a verticalplane relatively to points of attachment of said adjustable link meansto the seat frame (5).
 4. A seat arrangement according to claim 2 or 3,wherein the two adjustable link means (9) linked to each side rail (1)are linked by a common mounting bracket (7) spanning pins of attachmentof the adjustable link means (9) to the side rails (1).
 5. A seatarrangement according to anyone of claims 1-3, wherein said adjustablelink means are Bowden cables.